Method for producing an electrical contact and terminal board



Oct. 5, 1965 2. R. SMITH 3,210,453

METHOD FOR PRODUCING AN ELECTRICAL CONTACT AND TERMINAL BOARD Filed Oct. 20, 1961 2 Sheets-Sheet l INVENTOR Zeke R. Smith ORNEYJ Oct. 5, 1965 2. R. SMITH- 3,210,453

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INVENTOR Zeke R. Smith BY M g ,Q z

ATTORNEYS United States Patent 3,210,453 NETHGD FUR PRQDUCING AN ELECTRKCAL C(BNTACT AND TERMENAL BOARD Zeke R. Smith, Princeton, Ind, assignor to American Machine & Foundry Company, a corporation of New Jersey Filed 0st. 20, 1961, Ser. No. 146,607 (Claims. (Cl. 264-272) This invention relates to the manufacture of electrical assemblies, and particularly assemblies such as the small contact and terminal boards employed in miniature relays and the like, by combined plastic molding and metalworking techniques.

In various types of electrical devices, it has long been common practice to employ for various purposes an assembly comprising a supporting body of molded insulating material and a plurality of electrically conducting elements embedded in the supporting body and having portions projecting therefrom. One example of such an assembly is the contract and terminal board employed in many types of electromagnetic relays. Such an assembly has a self-supporting molded body of electrical insulating material in which are embedded the strips of metal which carry the stationary contacts of the relay. Advantageously, such strips project in opposite directions from two sides of the body of insulating material, the stationary contacts of the relay being located on one side of that body and the portions of the strips of metal on the other side being employed as the terminals to which the lead wires are connected, as by soldering. In cases where such an assembly is relatively large, the problems of manufacture are not unusually severe and prior art workers have proposed numerous procedures for satisfactorily producing products of this type. In recent years, however, manufacturers of relays and like devices have been called upon to provide smaller and smaller products. Thus, a typical contact and terminal board for one miniature relay now offered on the market calls for a terminal board which measures only one inch by three-quarters of an inch, yet must carry fourteen terminal elements. Recognizing that, by present day standards, this is not an unusually small device, it will be understood that the trend toward compactness presents manufacturing problems not solved by methods heretofore employed when constructing relatively large relays and the like.

When manufacturing a terminal board for a small relay, one of the particularly severe problems encountered is the tendency for any plastic molding procedures to produce flash on surface areas of the metal, electrically conductive elements of the structure which, for satisfactory operation of the relay or the like, must be clean and free from foreign material. In the manufacture of relatively large products, it is not an unusually difficult task to clean up such assemblies, removing the flash manually. However, such a practice becomes completely impractical when relatively small assemblies are involved. Manual removal of flash, in particular, is too time consuming and expensive to be acceptable.

Another problem encountered in manufacturing composite assemblies, embodying both a supporting body of plastic, insulating material and a plurality of metallic elements, such as contact and terminal strips, embedded in the supporting body and projected therefrom, is quickly encountered as the size of the finished structure is de creased. This problem arises because of the necessity for using molding techniques, to produce the plastic supporting body, involving mold parts provided with recesses into which the relatively small metal elements project. Obviously, it is necessary that the small metal elements be precisely aligned with the recesses which are to accom- 3,2 1,453 Patented Get. 5, 1965 modate them as the mold is closed, else jamming occurs, the small metal elements are bent and ruined, and the mold parts are damaged.

A general object of the present invention is to provide an improved method for producing composite electrical assemblies, particularly miniature assemblies such as contact and terminal boards for relays, which method evercomes the problems mentioned above.

Another object is to provide a method for molding a composite structure, involving a plastic supporting body from which a plurality of contact-carrying arms, terminals or the like project, without the formation of flash on the projecting elements.

A further object is to provide such a method which has the additional advantage of accomplishing positive, automatic alignment of the projecting elements in the recesses in the mold parts employed.

In order that the manner in which these and other objects are attained in accordance with the invention can be understood in detail, reference is had to the accompanying drawings, which form a part of this specification and wherein:

FIG. 1 is a perspective view of a contact and terminal board assembly constructed in accordance with one embodiment of the invention;

FIG. 2 is a perspective view of a contact-carrying and terminal element employed in making the device of FIG. 1 in accordance with the method of the present invention;

FIGS. 3 and 4 are sectional views illustrating parts of a mold employed in accordance with the invention and showing one of the elements of FIG. 2 in elevation in its proper place with respect to the mold parts, the mold parts being illustrated in spaced apart relation, before closing of the mold;

FIGS. 5 and 6 are sectional views, corresponding to FIGS. 3 and 4, respectively, illustrating the parts after the mold has been closed and filled; and

FIG. 7 is a fragmentary perspective view, enlarged with respect to FIG. 1, of a portion of the structure illustrated in FIG. 1.

Before proceeding with a detailed description of the method of the present invention, general reference will be made to the contact and terminal board assembly shown in FIG. 1 because this assembly is typical of the type of product which can be produced in accordance with the invention. Here, it will be seen that the assembly includes an integrally molded supporting body 1 of suitable insulating material within which are embedded a plurality of elongated metallic elements 2. Elements 2 are all identical, each having an intermediate portion embedded within the supporting body 1, a contact-carrying tip portion 3 projecting outwardly from one face 4 of the body 1, and a terminal portion 5 projecting from the opposite face of body 1. The major faces of the body 1, including face 4-, are parallel, and all of the elements 2 project at right angles to these major faces, so as to be parallel to each other. The utility of an assembly of this type in the manufacture of electrical products, such as relays, will be readily understood by those skilled in the art. It will thus be recognized that the stationary contacts (not shown) of a relay can be mounted in the openings 6 of tipportions 3 and that the usual lead wires (not shown) can be soldered or otherwise connected to the projecting portions 5 of the elements 2.

In the prior art, it has frequently been the practice to manufacture assemblies of this type by conventional pla'stic molding techniques. Thus, referring to FIG. 3, cooperating mold parts 8 and 9 may be used, mold part 8 having a recess 10 and mold part 9 having a recess 11, the two recesses combining to define a hollow mold cavity when the mold is closed by bringing edge portions 12 and 13 of the mold parts together. It will be clear that the mold cavity is bounded in part by opposing major surfaces 14 and corresponding respectively to the major faces of the supporting body 1 of the assembly illustrated in FIG. 1. The purpose of the molding procedure is of course to form the insulating material to the final shape for the supporting body 1, and also to accomplish secure embedding of the metal elements 2 in the supporting body. Accordingly, mold part 8 is necessarily provided with a plurality of elongated recesses 16 all of which are parallel to each other and Which extend at right angles to the face 14. Similarly, mold part 9 is provided with a plurality of recesses 17, all of which are parallel and extend at right angles to face 15. Recesses 16 are so located as to be aligned, relative to the mold cavity, with the proper positions for contact-carrying portions 3. correspondingly, recesses 17 are properly disposed in alignment with the positions for terminal portions 5 of the elements 2.

In accordance with conventional molding practices, mold part 9 may be a stationary part and mold part 8 may be movable toward and away from the mold part 9 in order that the mold can be opened and closed. In order that proper alignment between mold parts 8 and 9 shall be assured, and proper alignment of recesses 16 and 17 therefore maintained throughout the process, any suitable guide means can be used, cooperating between the two mold parts. Thus, a guide pin 18 can be fixed to mold part 9 so as to project into a guide bore 19 in mold part 8.

Prior to adoption of the present method, the use of the molding procedures of the type just referred to, to produce an article such as that seen in FIG. 1, has presented certain serious problems. First, assuming that the mold is closed and the moldable insulating material employed for the supporting body 1 has been introduced to the mold cavity under pressure, there is a distinct tendency for the insulating material to escape from the mold cavity into the recesses, such as recesses 16, so as to form objectionable flash on those portions of the metallic elements projecting into the recesses. Next, there has been a tendency for projecting portions of the metal elements to catch or jam on the mold parts, particularly during the latter stages of closing of the mold, so that the metal elements are so seriously distorted and damaged as to render the product unusable and, frequently, to damage the mold parts. Both of these disadvantages are overcome by the present methed as will now be described in detail.

Referring to FIG. 2, it will be seen that the metal elements 2 employed in accordance with this method have an enlarged body portion 20. Body portion 211 and contact-carrying tip portion 3 are both of rectangular transverse cross section, but the body portion 20 is substantially thicker and wider than is tip portion 3. Accordingly, body portion 20 joins tip portion 3 in a shoulder 21 and it will be noted that the shoulder 21 extends transversely of the metal element, at right angles to the longitudinal axis thereof, and presents a fiat face directed toward the free tip of portion 3. The shoulder 21 can be considered as having rectangularly extending edges, indicated at 22.

Body portion 20 is also of larger cross section than is the terminal portion 5 and the body portion therefore joins terminal portion 5 at a transversely extending shoulder, indicated at 23. The free tip of contact-carrying portion 3 is rounded in plan and is chamfered or tapered on both of its major faces, as indicated at 24.

Elements 2 are formed of any suitable metal having both good electrical conducting characteristics and the ability to be coined, that is, to be shaped by cold flow when subjected to a heavy squeezing action. Thus, for ex ample, elements 2 can be of brass suitably electroplated with tin or cadmium. Alternatively, these elements can be formed of any of the usual nickel-silver alloys.

Referring again to FIG. 3, it Will be seen that the body portions 20 of the elements 2 have a length materially greater than the spacing between mold faces 14 and 15 when the mold is closed. Hence, when the mold is slight- 4 1y open, as illustrated in FIG. 3, with a distinct gap between faces 12 and 13, the ends of body portions 20 engage bot-h faces 14 and 15, respectively, as shown.

Each recess 16 can be considered as having a mouth which opens through face 14 of mold part 8. As an important feature of this invention, such mouth is defined by wall portions, indicated at 25 in FIGS. 3 and 4-, which converge from face 14 inwardly to the main body of recess 16. Recognizing that FIG. 4 is a sectional view taken along line 44, FIG. 3, and comparing FIGS. 3 and 4, it will be understood that the converging Walls 25 define a mouth which has a rectangular transverse cross section. It will also be noted that the converging walls 25 are each disposed at an oblique angle, advantageously about 45 de grees, with respect to the longitudinal axis of recess 16. The dimensions of the mouth defined by converging walls 25 are made such, relative to the size of body portions 20 of elements 2, that the edges 22, defining the surface presented by shoulder 21, fall slightly within the open mouth and therefore engage the wall portions 25 in line contact, when the elements 2 and the mold parts are positioned with respect to each other in the manner shown in FIGS. 3 and 4.

With mold parts 8 and 9 and elements 2 all provided in the manner above described, the mold is completely opened by displacing mold part 8. All of the elements 2 to be employed are then loaded into the mold manually, the terminal portions 5 being inserted into recesses 17 in mold part 9 so that shoulders 23 engage or seat against face 15. Mold part 8 is then returned to the position seen in FIGS. 3 and 4, the guide means comprising pin 18 and bore 19 assuring that the contact-carrying tip portions 3 of elements 2 are substantially aligned with the respective recesses 16 in mold part 8. Since the tips of portions 3 are rounded in plan and provided with chamfered portions 24, the portions 3 successfully enter recesses 16 without catching or jamming. Further closing of the mold brings edges 22 into contact with the corresponding converging wall portions 25. Since, for each recess 16, there are four wall portions 25, all converging and arranged rectangularly, contact of edges 22 with wall portions 25 acts to center the contact-carrying portions 3 of elements 2 with respect to the recesses 16 as the mold is closed.

Line contact between the straight edges 22 and the flat, converging wall portions 25 establishes an effective seal between the mold cavity and the recesses 16. Further, this seal is established as soon as contact occurs, so that it exists at a time when mold parts 8 and 9 are still spaced a material distance apart.

At any suitable stage in the molding procedure, and by any conventional method, there is introduced into the mold cavity a quantity of moldable electrical insulating material adequate to completely fill the mold cavity when the mold is closed. Thus, any suitable resinous molding composition, either thermosetting or thermoplastic, can be successfully employed in accordance with this method. In this case, suitability depends upon such characteristics as moldability, electrical insulating properties and mechancal strength, and not upon the novel features of the present method. Advantageously, however, a thermosetting material is employed, and transfer molding techniques followed, the hot, still fluid molding material being forced from a transfer pot into the mold cavity when the mold is fully closed.

Since an effective seal between the mold cavity and recesses 16 is provided by engagement of edges 22 with wall portions 25, the molding composition is prevented from escaping into recesses 16. Because the length of body portions 20 of elements 2 is materially greater than the ultimate spacing between mold faces 14 and 15, when the mold is closed, it follows that closing of the mold must accomplish deformation of the metal of body portions 211. It will be noted that the portions 20 are of substantial thickness and width and therefore will exhibit no tendency to bend or otherwise deform within the mold cavity under the pressure applied by the mold parts 8 and 9. Deformation which does occur is confined to the portions of bodies at shoulders 21. This deformation is exhibited as a coining operation, the metal of body portions 20 at shoulder 21 being caused by the molding pressure to flow into conformity with the converging wall portions 25. Advantageously, the length of body portions 20 is so selected that there will be adequate surplus metal to allow the coining operation to taper the entire face of shoulder 21 on each of the body portions 20. Accordingly, when the mold is completely closed, as seen in FIGS. 5 and 6, the pins of body portions 20 which were defined by shoulders 21, initially, have been reshaped to provide slanting surfaces a conforming completely to the converging wall portions 25. The mold cavity is of course completely filled with the molding composition, as indicated at 26, but none of the molding material extends as flash over any portion of the contact-carrying portion 3 of the elements 2. Thus, as will be clear from FIGS. 1 and 7, the coined, converging surfaces which connect the enlarged body portions 20 to portions 3 project cleanly from the flat surface 4 of supporting body 1. It will accordingly be apparent that composite assemblies of the type illustrated in FIG. 1 can be produced in accordance with this method without any requirement for hand finishing, insofar as the removal of mold flash from the small metallic elements is concerned.

It will be understood that, when the contact and terminal board assembly of FIG. 1 is for use in very small electromagnetic relays, the metal elements 2 are quite thin. Typically, contact-carrying portions 3 may be on the order of .02 inch in thickness and on the order of .085 inch in width. Further, it will be understood that, for purposes of economy, it is desirable to produce more than one (usually on the order of six) of the assemblies seen in FIG. 1 in a single molding operation. Thus, if six of the assemblies are to be molded at once, eighty-four of the projecting portions 3 will be involved and all must be so accurately aligned with their corresponding recesses 16, in the mold part 8, that none of the projecting portions 3 catches or jams during closing of the mold. The problem of satisfactory alignment of the projecting portions 3 is complicated by the fact that the recesses 16 have transverse cross sections only slightly larger than the transverse cross section of the portions 3. Thus, a very close fit is involved, so that the alignment requirements are severe. Because of this situation, the provision of chamfered portions 24 on the tip of each of the portions 3, in view of the rounded plan form of these tip portions, is important because it serves to guide the portions 3 smoothly and positively into the recesses 16. In actual practice, however, cooperation of shoulder edges 22 with the converging wall portions 25 has been found necessary in order to attain satisfactory operation of the method. It is this cooperation which assures that final closing of the mold can be accomplished without undue distortion of the small metallic elements.

In the embodiment of the invention illustrated, the elements 2 are hand-loaded into the mold, this operation being accomplished by inserting portions 5 into the recesses 17 of mold part 9. Because of this, and because of the fact that it is not critical to completely avoid formation of flash on the terminal portions 5, converging wall portions equivalent to portions 25 are not provided at the mouths of recesses 17, and the ends 23 of enlarged body portions 20 of elements 2 remain as simple transverse shoulders in the finished article. It will be understood, however, that, in other composite assemblies than the one shown in FIG. 1, it can be desirable to employ converging wall surfaces at the mouths of recesses 17 so as to effect coining of the end 23 of each of the body portions 20.

As shown in FIG. 2, each of the body portions 20 is provided with a central aperture 27. Body portions 20 are materially thicker than are portions 3 and 5, this difference in thickness being on the order of from one third to one-half, for example. Similarly, the additional width of elements 2 at body portions 20 is made material. Accordingly, in the finished assembly as seen in FIGS. 1 and 7, satisfactory strength and rigidity of the small metal elements 2 is attained because the materially enlarged portions 20 are rigidly embedded in the body 1 of insulating material, it being understood that the entire body 1 is integral and includes portions extending through the apertures 27 in the bodies 20.

What is claimed is:

1. The method for producing an electrical contact and terminal board of the type comprising a supporting body of electrical insulating material and a plurality of parallel contact and terminal elements each comprising a body portion embedded in the supporting body, a first tip portion projecting from one face of the supporting body and a second tip portion projecting from the opposite face of the body, com-prising providing a mold comprising a first and a second mold part operative when closed to define a hollow mold cavity of the shape and size of the supporting body to be molded, said cavity being bounded by two opposing surfaces each presented by a different one,

of said mold parts and corresponding to the faces of the supporting body from which the first and second tip portions project, said opposing surfaces being spaced apart by a predetermined distance when the mold is closed,

said first mold part being provided with a plurality of elongated parallel recesses equal in number to the first tip portions of the contact and terminal elements, said second mold part being provided with a plurality of elongated parallel recesses each disposed to be aligned with a different one of the recesses in said first mold part when the mold is closed, said recesses all extending at right angles to said opposing surfaces, said recesses of said second mold part each having a mouth opening through the one of said opposing surfaces presented by said second mold part, each of said mouths being defined by wall portions converging from said one opposing surface inwardly to the main body of the correspond ing one of said recesses, loading into said first mold part a plurality of contact and terminal elements formed of a coinable metal, each of said elements comprising an enlarged body portion having a length slightly greater than said predetermined distance, a first tip portion projecting from one end of said enlarged body portion and dimensioned to be received in said recesses of said first mold part, and a second tip portion projecting from the other end of said enlarged body portion and dimensioned to be received in said recesses of said second mold part, said enlarged body portion joining said second tip portion at a transversely extending shoulder, said loading step being accomplished by inserting said first tip portions of said elements each into a different one of said recesses of said first mold part and causing the corresponding ends of the enlarged body portions of said elements to engage the one of said opposing surfaces presented by said first mold part, causing relative movement between said mold parts in a direction parallel to the longitudinal axes of said recesses, while maintaining the recesses of the two mold parts in alignment, until the edges defining said transversely extending shoulders of each of said elements engage the mouth-defining wall portions of the corresponding recess in said second mold part in at least substantially line contact to separate the interiors of the recesses in said second mold part from the hollow cavity of the mold,

said converging wall portions of said mouth of each of said recesses being operative to guide an end of each of said second tip portions into each of said recesses during said relative movement between said mold parts, and said converging wall portions further being operative to accurately center said enlarged body portions relative to said recesses and said wall portions when said mold parts are positioned with said wall portions in substantial line contact with said shoulders, causing further relative movement between said mold parts in said direction to close the mold and coin the ends of said enlarged body portions at said transversely extending shoulders of said elements into conformity with said mouth-defining wall portions, and filling the hollow cavity of the mold with a moldable electrical insulating material,

said coining establishing an effective seal to prevent entry of said moldable electrical insulating material into said recess. 2. A method in accordance with claim 1 and wherein said mouth-defining wall portions are flat and disposed at oblique angles to the longitudinal axis of the recess with which they are associated, the transverse cross section of said mouths being rectangular, and the edges of each of said shoulders defining a rectangle similar to the rectangular cross section of the corresponding one of said months. 3. In the production of a composite electrical assembly of the type described, the improvement comprising providing a mold including rigid, relatively movable mating parts defining a hollow mold cavity of predetermined width,

one of said parts presenting a face defining part of said cavity, said one part having a recess extending away from said face and having a tapered mouth which opens through said face, said mouth having a cross section of predetermined shape and being defined by wall portions which converge from said face inwardly with respect to said recess, mounting in another of said mold parts an elongated electrically conductive element of a coinable metal, said element being mounted in a position to extend across said predetermined width of the mold cavity and including both a body portion of enlarged transverse cross section and a tip portion of smaller transverse cross section projecting from said body portion, said body portion joining said tip portion in a transverse shoulder having edges defining a transverse surface similar to but smaller than the maximum transverse cross section of said mouth,

the length of said body portion being slightly greatly than said predetermined Width of said mold cavity and said element being engaged with said other mold part to prevent longitudinal movement of said element toward said other mold part, causing relative movement between said mold parts along a line parallel to the longitudinal axis of said element, with said tip portion of said element substantially aligned with said recess, and thereby causing said tip portion of said element to enter said recess and said shoulder to center said month,

said converging wall portions being operative to guide an end of said tip portion into said recess, causing further relative movement between said mold parts, along said line, to close the mold,

said edges of said shoulder engaging said mouthdefining wall portions in at least substantially line contact during such further relative movement and such further movement causing the end of said main body portion of said element to be coined, engagement of the edges of said shoulder with said mouth-defining wall portions serving to accomplish precise centering of said tip portion and said shoulder with respect to said recess as the mold is closed, and filling the hollow cavity of the mold with a moldable electrical insulating material,

said coining establishing an eifective seal to prevent entry of said moldable electrical insulating material into said recess. 4. A method for producing a composite electrical assembly in accordance with claim 3 and wherein said tip portion is a thin, flat, strip-like projection and said body portion is substantially thicker,

said body and tip portions having similar rectangular transverse cross sections, and said recess has a rectangular transverse cross section only slightly larger than that of said tip portion. 5. A method for producing a composite electrical assembly in accordance with claim 4 and wherein the major faces of the free end of said tip portion are chambered to facilitate guiding said tip portion through said mouth and into said recess References Cited by the Examiner UNITED STATES PATENTS 2,040,674 5/36 Severance et al. 18-59 XR 2,135,570 11/38 Ellis 264-276 2,242,117 5/41 English et al. 18-59 2,266,432 12/41 M-orin et al. 18-59 2,857,583 10/58 Markley et al 339-198 2,864,130 12/58 Beare 264-276 2,911,615 11/59 Popejoy et al. 339-198 2,949,641 8/60 Quackenbush 18-59 3,090,108 5/63 Gifiord 264-276 ROBERT F. WHITE, Primary Examiner.

MICHAEL V. BRINDISI, ALEXANDER H.

BRODMERKEL, Examiners. 

1. THE METHOD FOR PRODUCING AN ELECTRICAL CONTACT AND TERMINAL BOARD OF THE TYPE COMPRISING A SUPPORTIN BODY OF ELECTRICAL INSULATING MATERIAL AND A PLURALITY OF PARALLEL CONTACT AND TERMINAL ELEMENTS EACH COMPRISING A BODY PORTION EMBEDDED IN THE SUPPORTING BODY, A FIRST TIP PORTION PROJECTING FROM ONE FACE OF THE SUPPORTING BODY AND A SECOND TIP PORTION PROJECTING FORM THE OPPOSITE FACE OF THE BODY, COMPRISING PROVIDING A MOLD COMPRISING A FIRST AND A SECOND MOLD PART OPERATIVE WHEN CLOSED TO DEFINE A HOLLOW MOLD CAVITY OF THE SHAPE AND SIZE OF THE SUPPORTING BODY TO BE MOLDED, SAID CAVITY BEING OUNDED BY TWO OPPOSING SURFACES EACH PRESENTED BY A DIFFERENT ON OF SAID MOLD PARTS AND CORRESPONDING TO THE FACES OF THE SUPPORTING BODY FROM WHICH THE FIRST AND SECOND TIP PORTIONS PROJECT, SAID OPPOSING SURFACES BEING SPACED APART BY A PREDETERMINED DISTANCE WHEN THE MOLD IS CLOSED, SAID FIRST MOLD PART BEING PROVIDED WITH A PLURALITY OF ELONGATED PARALLEL RECESSES EQUAL IN NUMBER TO THE FIRST TIP PORTIONS OF THE CONTACT AND TERMINAL ELEMENTS, SAID SECOND MOLD PART BEING PROVIDED WITH A PLURALITY OF ELONGATED PARALLEL RECESSES EACH DISPOSED TO BE ALIGNED WITH A DIFFERENT ONE OF THE RECESSES IN SAID FIRST MOLD PART WHEN THE MOLD IS CLOSED, SAID RECESSES ALL EXTNDING AT RIGHT ANGLES TO SAID OPPOSING SURFACES, SAID RECESS OF SAID SECOND MOLD PART EACH HAVING A MOUTH OPENING THROUGH THE ONE OF SAID OPPOSING SURFACES PRESENTED BY SAID SECOND MOLD PART, EACH OF SAID MOUTHS BEING DEFINED BY WALL PORTIONS CONVERGING FOM SAID ONE OPPOSING SURFACE INWARDLY TO THE MAIN BODY OF THE CORRESPONDING ONE OF SAID RECESSES, LOADING INTO SAID FRIST MOLD PART A PLURALITY OF CONTACT AND TERMINAL ELEMENTS FORMED OF A COINABLE METAL, EACH OF SAID ELEMENTS COMPRISING AN ENLARGED BODY PORTION HAVING A LENGTH SLIGHTLY GREATER THAN SAID PREDETERMINED DISTANCE, A FIRST TIP PORTION PROJECTING FROM ONE END OF SAID ENLARGED BODY PORTION AND DIMENSIONED TO BE RECEIVED IN SAID RECESSES OF SAID FRIST MOLD PART, AND A SECOND TIP PORTION PROJECTING FROM THE OTHER END OF SAID ENLARGED BODY PORTION AND DIMENSIONED TO BE RECEIVED IN SAID RECESSES OF SAID SECOND MOLD PART, SAID ENLARGED BODY PORTION JOINING SAID SECOND TIP PORTION AT A TRANSVERSELY EXTENDING SHOULDER, SAID LOADING STEP BEING ACCOMPLISHED BY INSERTING SAID FIRST TIP PORTIONS OF SAID ELEMENTS EACH INTO A DIFFERENT ONE OF SAID RECESS OF OF SAID FIST MOLD PART AND CAUSING THE CORRESPONDING ENDS OF THE ENLARGED BODY PORITONS OF SAID ELEMENTS TO ENGAGE THE ONE OF SAID OPPOSING SURFACES PRESENTED BY SAID FIRST MOLD PARTS, CAUSING RELATIVE MOVEMNT BETWEEN SAID MOLD PARTS IN A DIRECTION PARALLEL TO THE LONGITUDINAL AXES OF SAID RECESSES, WHILE MAINTAINING THE RECESSES OF THE TWO MOLD PARTS IN ALIGNMENT, UNTIL THE EDGES DEFINING SAID TRANSVERSELY EXTENDING SHOULDERS OF EACH OF SAID ELEMENTS ENGAGE THE MOUTH-DEFINING WALL PORTIONS OF THE CORRESPONDING RECESS IN SAID SECOND MOLD PART IN AT LEAST SUBSTANTIALLY LINE CONTACT TO SEPARATE THE INTERIORS OF THE RECESSES INSAID SECOND MOLD PART FROM THE HOLLOW CAVITY OF THE MOLD, SAID CONVERGING WALL PORTIONS OF SAID MOUTH OF EACH OF SAID RECESSES BEING OPERATIVE TO GUIDE AN END OF EACH OF SAID SECOND TIP PRTIONS INTO EACH OF SAID RECESSES DURING SAID RELATIVE MOVEMENT BETWEN SAID MOLD PARTS, AND SAID CONVERGING WALL PORTIONS FURTHER BEING OPERATUVE TO ACCURATELY CENTER SAID ENLARGED BODY PORTIONS RELATIVE TO SAID RECESSES AND SAID WALL PORTIONS WHEN SAID MOLD PARS ARE POSITIONED WITH SAID WALL PORTIONS IN SUBSTANITAL LINE CONTACT WITH SAID SHOULDERS, CAUSING FURTHER RELATIVE MOVEMENT BETWEEN SAID MOLD PARTS IN SAID DIRECTION TO CLOSE THE MOLD AND COIN THE ENDS OF SAID ENLARGED BODY PORTIONS AT SAID TRANSVERSELY EXTENDING SHOULDERS OF SAID ELEMETNS INTO CONFORMITY WITH SAID MOUTH-DEFINING WALL PORTIONS, AND FILLING THE HOLLOW CAVITY OF THE MOLD WITH A MOLDABLE ELECTRICAL INSULATING MATERIAL, SAID COINING ESTEABLSHING AN EFFECTIVE SEAL TO PREVENT ENTRY OF SAID MOLDABLE ELECTRICAL INSULATING MATERIAL INTO SAID RECESS. 